Loud speaker magnetic assembly and pot



March 21, 1967 D. M. COLLINS 3,310,639

LOUD SPEAKER MAGNETIC ASSEMBLY AND POT Filed Jan. 25, 1964 INVENTOR.

United States Patent 3,310,639 LOUD SPEAKER MAGNETIC ASSEMBLY AND POT David M. Coilins, Hinsdale, 11]., assignor to York Tool and Manufacturing Co., Eellwood, 111., a corporation of Illinois Filed Ian. 23, 1964, Ser. No. 339,804 8 Claims. (Cl. 179-420) This invention relates to loud speakers and analogous devices, and is directed more particularly to the magnetic assembly comprising a permanent magnet and a housing or holder therefor, commonly termed the pot, used in such devices.

Speaker pots are used in large volume and the cost of production thereof is an important consideration. My invention is directed to a pot which is highly eflicient in use and can be produced in volume at comparatively low cost. More particularly, the pot of my invention may be produced at high speed by punch presses, using dies and mandrels, from magnetic sheet material, such as cold rolled sheet steel. The housing or holder for the magnet is so constructed as effectively to retain the magnet properly positioned therein while accommodating minor inaccuracies and also assuring adequate magnetic flux density across the annular space or gap for the voice coil of the speaker. Further objects and advantages of my invention will appear from the detailed descript-ion.

In the drawings:

FIGURE 1 is a sectional view of a loud speaker embodying the magnetic assembly and pot of my invention, with certain parts shown in elevation;

FIGURE 2 is a plan view of a strip from which the pot of my invention is formed, looking at the face of the strip which is to become the inner surface of the pot holder.

FIGURE 3 is a sectional view taken substantially on line 3-3 of FIGURE 2;

FIGURE 4 is a side view of the pot holder, without the cap, formed from the strip of FIGURES 2 and 3;

FIGURE 5 is a sectional view taken substantially on line 55 of FIGURE 4;

FIGURE 6 is an exploded view of the parts of the magnetic assembly; and

FIGURE 7 is an axial sectional view of the assembly comprising the parts shown in FIGURE 6, the magnet being shown in elevation.

In FIGURE 1 I have shown the pot of my invention as applied, by way of example, to a loud speaker of conventional type, except as to the pot. The speaker comprises a frame 8 on which are mounted a diaphragm 9, of conical form, and. a guide 10 for the neck 11 of the diaphragm. Neck 11 extendsinto the annular space or gap at the upper end of the magnetic assembly or pot 12, to be described in detail later, and carries the usual voice coil 13. The speaker frame 8 is provided with a flat base 14 to which the assembly or pot 12 is secured in a suitable manner, convenient-1y by staking. It will be understood that the magnetic assembly or pot of my invention is not limited to loud speakers and may be used for any purpose for which it is suitable.

The pot 12 comprises a housing or holder 15 and a cylindrical permanet magnet 16 mounted therein. The latter preferably is made of Alnico V having a composition of substantially 8% aluminum, 14% nickel, 24% cobalt, 3% copper and 51% iron. The magnet 16 may be a casting which is ground to the desired diameter, as is known.

The holder 15 is formed of a resilient magnetic material which possesses substantial mechanical strength,

3,310,639 Patented Mar. 21, 1967 such as cold rolled steel of suitable gauge. In forming the holder a flat strip of cold rolled steel, of appropriate width and length and thickness, is shaped, conveniently between opposed dies, to the cross sectional form shown in FIGURES 2 and 3. The strip so shaped comprises an upper flange 17, a lower flange 18 and an intervening body portion 19 which is off-set outwardly relative to flanges 17 and 18 and is connected thereto by up er and lower shoulders 20 and 2 1, respectively, inclined toward body portion 19. The upper flange 17 preferably, but not necessarily, is off-set outwardly to a slight extent relative to the lower flange 13 and is of greater height than the latter flange, for a purpose to be explained presently.

The strip of FIGURES 2 and 3 is formed by appropriate die and mandrel means into a split ring the ends of which may be spaced a slight distance apart providing a narrow slot-like opening between them. The resultant split ring or holder 15 comprises an upper circular collar 17a, a lower circular collar 18a and an intervening body portion 19a offset radially outward relative to collars 17a and 18a. The upper collar 17a is connected to body portion 19a by an interior downwardly and outwardly inclined shoulder 20a and the lower collar 18a is connected to body portion 10a by a shoulder 21a which is inclined downwardly and inwardly to the opening defined by the lower collar 180. As above noted, in the strip of FIGURES 2 and 3, the upper flange 17 preferably is off-set outwardly to a slight extent relative to the lower flange 18. In forming the strip to provide the split ring of FIGURES l and 4 to 7, inclusive, the upper and lower flanges 17 and 18 thereof are shaped to provide coaxial upper and lower rings or collars. In the resultant split ring or holder 15 the upper collar 17a is of somewhat greater interior diameter than the lower collar 18a and is also of greater height than collar 18a. 1

As will be understood from the above, the holder 15 is in the form of a split ring, the ends of which may be spaced a slight distance apart, and comprises the upper and lower collars 17a and 18a and the intervening body portion 19a which is off-set radially outward relative to the collars. Preferably, though not necessarily, the lower end of the holder 15 is closed, either partially or completely, by a magnetic element upon which the flat lower end of magnet 16 seats. The magnetic element referred to is suitably attached to the lower collar 18a and may conveniently be in the form of a cap 22, formed of cold rolled steel and provided with an upwardly extending circumferential flange 23 which has a friction fit over the lower collar 13a. The holder 15, including the cap 22 or other suitable magnetic element, is cadmium plated to guard against rust or corrosion.

Preferably, though not necessarily, the magnet 16 and holder 15 are assembled and the magnetic assembly is secured to the speaker in a single operation. Preliminary to such operation, the upper collar 17a of holder 15 is inserted through a corresponding collar 14a of base 14 of the speaker frame 8, with collar 14a seating on the upper shoulder 20a and collar 17a extending above the upper faceof base 14. Thereafter, by means of a suitable die and plunger assembly, the magnet is accurately centered relative to holder 15, the upper collar 17a is staked to base 14 and the magnet v16 is forced into the lower collar 18a to position with its lower end seating on the magnetic element or cap 22 attached to collar 18a. In this manner the magnetic assembly or pot 12 is assembled and is secured to the base of the speaker.

The magnet 16 is shown as being of a uniform diameter to have a press fit in lower collar 18a of holder 15. If the diameter of the magnet 16 is slightly oversize, or

the interior diameter of the collar 18a is slightly undersize, the holder will expand sutficiently to accommodate such inaccuracies. Such slight expansion of holder 15 is permitted by its split ring construction and by'the flange 23 of cap 22, when used, which will give slightly under the pressure exerted in forcing magnet 16 into collar 18a. The housing 15 then grips tightly the lower end portion of magnet 16 with a strong spring efiect and holds it securely in position. It is intended that the diameter of magnet .16 and the interior diameter of collar 18a be such that the magnet 16 will have a press fit in collar 18a, placing it under radial tension but without causing actual expansion thereof. In the event of slight inaccuracies requiring slight expansion of the collar 18a when the magnet 16 is forcibly inserted into it, such expansion can occur, as above stated. The forming of housing 15 as a split ring is advantageous in that it will accommodate slight inaccuracies in the parts and the same precision is not required as would be essential if the housing 15 were incapable of radial expansion when inserting the magnet 16. In the event the diameter of the magnet 16 is slightly undersize, or the interior diameter of collar 18a is slightly oversize, such that the magnet 16 has a snug, but not tight, fit in collar 18a, the magnetic attraction between magnet 16 and the magnet element, such as cap 22 or an equivalent thereof, will retain the magnet 16 properly posi tioned in the holder 15. In either case, assurance is had that the magnet 16 will not be displaced by jolts or jars to which the speaker may be subjected in handling or in shipment.

As will be understood from what has been said, the magnet .16 extends upwardly into the upper collar 17a in concentric spaced relation thereto. That provides an annular space or gap about the upper end of magnet 16, which space receives the neck 11 of diaphragm 9 with the voice coil 13 mounted thereon, as usual. The inclined shoulders a and 21a of the holder 15 have the advantage of imparting increased strength thereto for gripping the magnet with a spring action, as above explained. The lower shoulder 21a also has the further advantage of guiding the lower end of the magnet 16 to the opening of the lower collar 18a in the operation of assembling the holder 15 and the magnet 16, in the event of any slight misalignment of the parts.

The magnet 16 preferably is of uniform diameter, as above stated, but that is not'essential. Within the broader aspects of my invention the upper end portion of the magnet may be of different diameter than the body portion thereof. Assuming that the upper end portion of the magnet is of less diameter than the body portion thereof, the strip of FIGURE 2 and 3 is so formed that the upper collar 17a of the holder 15 is off-set inwardly relative to the lower collar 18a to an extent such that the desired air gap for the voice coil 13 is provided. It is preferred that the magnet 16 be of uniform diameter, as shown by way of example, to avoid the expense of precision grinding the upper end of the magnet to reduced diameter, or of applying to the upper end of the body of the magnet a tip of reduced diameter, as is known. Briefly, my invention comprehends a speaker pot in which the magnet 16 may be of either uniform diameter or of reduced diameter at its upper end, the holder 15 being so formed that the upper collar 17a thereof is of proper interior diameter to provide, with the upper end of the magnet, an appropriate annular gap or space for the voice coil 13.

It will be understood, as above indicated, that changes in detail may be resorted to 'without departing from the field and scope of my invention, and I intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred form only of my invention has been disclosed.

I claim:

1. In a speaker pot, a holder comprising a ring of resilient magnetic material split in the direction of its axis and formed to provide coaxial upper and lower collars with an intervening body portion off-set radially outward relative to said collars, and a magnet in said holder, the lower end portion of said magnet having a press fit in said lower collar and the latter being held by the inherent resiliency of said holder in gripping engagement about said lower end portionof said magnet, the upper end portion of said magnet extending into said upper collar in substantially concentric spaced relation there-to and the intermediate portion of said magnet being spaced radially inward from said body portion of said holder.

2. In a speaker pot, a holder comprising a ring of resilient magnetic material split in the direction of its axis and formed to provide coaxial upper and lower circular collars with an intervening body portion off-set radially outward relative to said collars, and a cylindrical magnet in said holder coaxial therewith and of a diameter approximately the same as the interior diameter of said lower collar, the lower end portion of said magnet having a press fit in said lower collar and the later being held by the inherent resiliency of said holder in gripping engagement about said lower end portion of said magnet, the upper end portion of said magnet extending into said upper collar in substantially concentric spaced relation thereto and the intermediate portion of said magnet being spaced radially inward from said body portion of said holder.

3. In a speaker pot, a holder comprising a ring of resilient magnet material split in the direction of its axis and formed to provide coaxial upper and lower collars with an intervening body portion offset radially outward relative to said collars, a magnet in said holder coaxial therewith and of a cross section at its lower end approximately the same as the opening of said lower collar, the lower end portion of said magnet having a friction fit in said lower collar, and a magnetic elementsecured to said lower collar extending radially inward thereofwith the lower end of said magnet seating on said element providing therewith magnetic means supplementing said friction fit for restraining said magnet against upward movement relative to said lower collar, the upper end portion of said magnet extending into said upper collar in substantially uniform spaced relation thereto and the intermediate portion of said magnet being spaced radially inward from said body portion of said holder.

4. In a speaker pot, a holder comprising a ring of resilient magnetic material split in the direction of its axis and formed to provide coaxial upper and lower circular collars with an intervening body portion off-set radially outward relative to said collars, a cylindrical magnet in said holder coaxial therewith and of a diameter approximately the same as the interior diameter of said lower collar, the lower end portion of said magnet having a friction fit in said lower collar, and a magnetic cap having a friction fit on said lower collar with the lower end of said magnet seating on said cap providing therewith magnetic means supplementing said friction fit for restraining said magnet against upward movement relative to said lower collar, the upper end portion of said magnet extending into said upper collar in substantially concentric spaced relation thereto and the intermediate portion of said magnet being spaced radially inward from said body portion of said holder.

5. In a speaker pot, a holder comprising a ring of resilient magnet material split in the direction of its axis .and having coaxial upper and lower circular collars and an intervening body portion, said upper collar having an interior diameter greater than that of said lower collar, the portions of said holder being free from each other at said split and a cylindrical magnet in said holder coaxial with said collars and of a uniform diameter approximately the same as the interior diameter of said lower collar, the lower end portion of said magnet hav ing a friction fit in said lower collar, the upper end 5 portion of said magnet extending into said upper collar in substantially concentric spaced relation thereto and the intermediate portion of said magnet being spaced radially inward from said intervening portion of said holder.

6. As a new article of manufacture, a holder for a speaker pot, said holder comprising upper and lower collars defining coaxial openings and having an intervening body portion olT-set radially outward relative to said collars, said holder being split in the direction of the axis of said openings and the portions of said holder being free from each other at said split.

7. As a new article of manufacture, a holder for a speaker pot, said holder comprising a ring of resilient magnet material split in the direction of its axis and having coaxial upper and lower circular collars the portions ofsaid holder being free from each other at said split, with an intervening body portion off-set radially outward relative to said collars, said upper collar having an interior diameter greater than that of said lower collar.

8. As a new article of manufacture, a holder for a speaker pot, said holder comprising a ring of resilient Y magnetic material split in the direction of its axis and having coaxial upper and lower circular collars with an intervening body portion, the portions of said holder being free from each other at said split, said upper collar having an interior diameter greater than that of said lower collar.

References Cited by the Examiner UNITED STATES PATENTS 9/1939 Sundstrom 179115.5 12/1950 Munson 179-1l5.5

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0n 3, 310, 639 March 21, 1967 David M. Collins d that error appears in the above numbered pat- It is hereby certifie at the said Letters Patent should read as ent requiring correction and th corrected below.

Column 4, lines 29 and 66, and column 5, line 15, for

"magnet", each occurrence, read magnetic column 5, lines 16 to 19, for "the portions of said holder being free from each other at said split, with an intervening body portion off set radially outward relative to said collars," read with an intervening body portion off-set radially outward relative to said collars, the portions of said holder being free from each other at said split,

Signed and sealed this 7th day of November 1967,

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, 11'.

Attesting Officer 

6. AS A NEW ARTICLE OF MANUFACTURE, A HOLDER FOR A SPEAKER POT, SAID HOLDER COMPRISING UPPER AND LOWER COLLARS DEFINING COAXIAL OPENINGS AND HAVING AN INTERVENING BODY PORTION OFF-SET RADIALLY OUTWARD RELATIVE TO SAID COLLARS, SAID HOLDER BEING SPLIT IN THE DIRECTION OF THE AXIS OF SAID OPENINGS AND THE PORTIONS OF SAID HOLDER BEING FREE FROM EACH OTHER AT SAID SPLIT. 